College of Physics & Electronic Information Enginerring, WenZhou University, WenZhou 325035, Peoples Republic of China.
J Mol Model. 2011 Apr;17(4):879-88. doi: 10.1007/s00894-010-0782-9. Epub 2010 Jul 1.
The stable structures and aromatic characters for three cationic X(3)(+) (X = Sc, Y, and La) and three relevant neutral X(3)Cl (X = Sc, Y, La) clusters are investigated at the DFT and post HF level of theory. The calculated results show that the X(3)(+) cations each has two stable structures: the regular trigon (D(3h)) and the line (D∞h) with the regular trigon (D(3h)) being the ground state, while for three neutral X(3)Cl clusters, Sc(3)Cl has three stable isomers: the trigon-pyramidal (C(3v)), bidentate (C(2v)-1), and C(2v)-2 structures, Y(3)Cl and La(3)Cl each has only two stable isomers: the trigon-pyramidal (C(3v)) and bidentate (C(2v)-1) structures. The ground states for three X(3)Cl species are all the bidentate (C(2v)-1) isomers. The calculations of the resonance energy (RE) and NICS show that trigonal X(3)(+) isomers exhibit higher degree of aromaticity. The detailed molecular orbital analyzes reveal that the isolated trigonal Sc(3)(+) and Y(3)(+) cations each has one delocalized π-type MO and shows single π-aromaticity, while the isolated trigonal La(3)(+) cation has one delocalized σ-type MO and shows single σ-aromaticity. The single π- or σ-aromaticity for X(3)(+) are attributed to the contributions mainly from the d AOs of the corresponding transition metal X atoms. However, when a singly negatively charged counterion Cl(-) is added to Sc(3)(+), Y(3)(+), and La(3)(+) cations respectively, the aromatic type for the two Sc(3)(+), Y(3)(+) units in the corresponding neutral Sc(3)Cl, Y(3)Cl complexes are changed from π-aromaticity into σ-aromaticity, whereas the σ-aromaticity of the La(3)(+) units in the La(3)Cl complex keeps unchanged in this process. Thus three Sc(3)(+), Y(3)(+), La(3)(+) units in the corresponding X(3)Cl complexes all have only one σ-type MO and exhibit single σ-aromaticity.
本文在密度泛函理论(DFT)和后 Hartree-Fock(HF)水平上研究了三种阳离子 X(3)(+)(X = Sc、Y 和 La)和三种相应中性 X(3)Cl(X = Sc、Y、La)团簇的稳定结构和芳香特征。计算结果表明,X(3)(+)阳离子各有两种稳定结构:规则三角(D(3h))和直线(D∞h),其中规则三角(D(3h))为基态,而对于三种中性 X(3)Cl 团簇,Sc(3)Cl 有三种稳定异构体:三角锥(C(3v))、双齿(C(2v)-1)和 C(2v)-2 结构,Y(3)Cl 和 La(3)Cl 各有两种稳定异构体:三角锥(C(3v))和双齿(C(2v)-1)结构。三种 X(3)Cl 物种的基态均为双齿(C(2v)-1)异构体。共振能(RE)和 NICS 的计算表明,三角 X(3)(+)异构体具有更高的芳香度。详细的分子轨道分析表明,孤立的三角 Sc(3)(+)和 Y(3)(+)阳离子各有一个离域的 π 型 MO,表现出单 π-芳香性,而孤立的三角 La(3)(+)阳离子有一个离域的 σ 型 MO,表现出单 σ-芳香性。X(3)(+)的单 π-或 σ-芳香性归因于相应过渡金属 X 原子的 d AOs 的贡献。然而,当一个单负电荷的抗衡离子 Cl(-)分别加到 Sc(3)(+)、Y(3)(+)和 La(3)(+)阳离子上时,相应中性 Sc(3)Cl、Y(3)Cl 配合物中两个 Sc(3)(+)、Y(3)(+)单元的芳香类型由 π-芳香性变为 σ-芳香性,而 La(3)(+)单元在 La(3)Cl 配合物中的 σ-芳香性在这个过程中保持不变。因此,相应 X(3)Cl 配合物中的三个 Sc(3)(+)、Y(3)(+)、La(3)(+)单元都只有一个 σ 型 MO,表现出单 σ-芳香性。